With recent spread of digital cameras and recent broadband networking of the Internet, the user can easily acquire many images by, for example, capturing an image from a digital camera, receiving an image attached to E-mail from his friend, and downloading a still picture or moving picture from a Web page. Thus, the user must manage many images.
FIG. 10 shows a display example of an information management window in a conventional system. By designating a folder in a tree view 101, the thumbnails of files in the folder can be displayed. Reference numeral 102 denotes a pull-down menu which can switch the display mode; and 103, a slide bar which can switch the thumbnail display size. If thumbnail images exist in an image file or another file, image management software uses them for display; if no thumbnail image exists, creates thumbnails from original images and displays a list of the thumbnails in a browser window (to be referred to as a BW hereinafter) 104. Reference numerals 105 denote buttons (“minimize”, “maximize”, and “close” from the left) which are normally installed and used to control an application window display.
When many images exist in the folder, as shown in FIG. 10, a scroll bar 106 is displayed beside the BW 104. By scrolling the window with the scroll bar, the user must confirm images of the BW 104 which cannot be confirmed with the screen. At this time, in order to give importance on presenting images as many as possible to the user, images may be reduced at the same magnification and displayed as shown in FIG. 11 or 12, instead of displaying thumbnail images at a fixed size. By this reduction display operation, the user can confirm a larger number of images at once. In reduction display, the user may manually reduce the display size to one as shown in FIG. 11 by using a slide bar 203 for adjusting the display size. Alternatively, the display mode may be switched on a pull-down menu 302 to automatically reduce and display images by software so as to display images as many as possible, as shown in FIG. 12.
By reducing the image size and displaying images in the above-described way, many images can be confirmed at once, and the list property is improved. However, if a displayed image decreases to a predetermined size or less, it becomes difficult to confirm the contents of the image. As a conventional coping method, the user can select one of two means “to manually cancel the automatic enlargement/reduction function” and “to open a viewer which allows confirming an original image”.
The method “to manually cancel the automatic enlargement/reduction function” is a process of returning the display in FIG. 11 or 12 to one in FIG. 10. Respective images increase in size, and ease of confirming images improves, but enlargement changes an image layout which has been presented. This will be easily understood considering switching from the display in FIG. 11 to that in FIG. 10. This method is suitable for confirming a single image or a few images. To confirm a plurality of images, a target image must be searched for because the layout which has been checked is lost. In the above-described example, as the number of images to be confirmed becomes larger, the search range becomes larger, and the burden on the user becomes heavier. This method impairs the merit of listing.
The method “to open a viewer which allows confirming an original image” provides a merit of reliably confirming an original image. However, even when the same window is switched, as shown in FIG. 13, or when the viewer is opened in another window, as shown in FIG. 14, the user who wants to easily confirm an image must execute a redundant operation such as switching of the window display from the viewer mode to the original mode in a pull-down menu 402 after confirmation, closing of another window 506 which displays an original window after confirmation, or switching of the window. In displaying an original image by the viewer, the user must wait for a process time for displaying an original image that is longer than a process time of displaying a thumbnail.
Display devices which list and display images in a folder by classifying images stored in a storage device into folders have become popular. In order to efficiently search many images for a necessary image, there is proposed                a display device which designates a condition for images to be displayed, and lists and displays (filters and displays) only images having a specific property.        
For example, Adobe Photoshop Album® available from Adobe Systems has a function of adding a “tag” to an image and displaying only images having a specific tag (see “‘Photoshop Album’ Classify By Adding Tag”, [online], [searched Sep. 1, 2004], Internet <URL: http://www.adobe.co.jp/products/photoshopalbum/overview/page2.html#2—4>). In order to easily know the type of image recorded in each folder when many folders exist, there is also proposed                a folder content outline display means which reduces and displays only a predetermined number of images in a folder as an outline of the folder.        
For example, Windows XP® available from Microsoft provides a function of displaying, on a folder icon, the thumbnails of some images contained in a folder by using a “reduced” view (see “‘Usability Improvements in Windows XP for Knowledge Workers’ File and Folder Management”, [online], [searched Sep. 1, 2004], Internet <URL:    http://www.microsoft.com/japan/technet/prodtechnol/winx ppro/evaluate/usbltyxp.asp#d).
This function displays schematic contents of only a designated folder when a folder is designated, or automatically displays schematic contents at a location near a folder name without specially designating one of a plurality of folders.
Schematic contents of a folder are conventionally acquired in an order from the first image in the folder or in a designated order, and images are reduced and created in order until the number of images reaches a predetermined value. When this technique and filtering display are adopted at the same time, an image which is designated by filtering so as not to be displayed is displayed in schematic contents of the folder.